I've also come across adding vinegar to the distilled water and passing it through
the heat exchanger, I've always assumed it to be 50/50 mix. Anyone else use
this or has anyone tried the kettle descalers which I think is Citric Acid based??

Sorry for the (incredibly) late reply but I only just looked at the topic. A while back I was technical manager for a club in manchester using a Magnum smoke machine and yes it got terribly clogged after about 9months of heavy use. In our circumstances it could have been due to the cheep fluid used.

I ended up unblocking it using fizzy water. I wouldn't suggest doing this unless you really cant do it any other way as I can't see it doing the heat exchanger any good at all. It did however get ours to last another 6 months or so before I left.

Greetings,
Working and servicing smoke machines another trick to try is a paperclip pushed down the nozzle, to clean the muck out. If the nozzle is really blocked a 1/8" drill bit works. On some machines the nozzle assembly unscrews so that you can see daylight through it.